Generally, for a magnetic head device using a detecting element that operates based on a GMR effect (giant magnetoresistance effect) or a tunnel effect, a sense current flows in a thicknesswise direction of the detecting element and the magnetic head is referred to as a current-perpendicular-to-the-plane (CPP)-type device.
The CPP-type magnetic head device includes a lower shield layer formed of a soft magnetic material on the bottom of a detecting element, and an upper shield layer formed of a soft magnetic material on the detecting element. A leakage magnetic flux from a magnetic recording medium in a middle region between both the lower shield layer and the upper shield layer is detected by the detecting element, so that magnetic information recorded on the magnetic recording medium may be read. To apply a current to the detecting element in a thicknesswise direction in this CPP-type magnetic head device, the detecting element may be electrically connected to the lower shield layer and the upper shield layer, and a current may be applied to the detecting element through the upper and lower shield layers.
However, according to the related art, a conductive layer (lead layer) that applies a current to a lower shield layer and an upper shield layer is generally provided at an inner side than a facing surface of a recording medium.
In a magnetic head device disclosed in JP-A-2001-307307, a portion of each of a lower shield layer and an upper shield layer continuously extends backward, which forms a conductive layer (lead layer). In a magnetic head device disclosed in JP-A-2002-25017, an upper shield layer and a lower shield layer are formed such that the lower shield layer has a larger area than the upper shield layer and a rear portion of the lower shield layer extends backward more than a rear portion of the upper shield layer, via-hole conductors are provided on the lower and upper shield layers, and a conductive layer (lead layer) that is electrically connected to each via-hole conductor is provided on an insulating layer covering the lower shield layer.
The lower shield layer and the upper shield layer have a function of transmitting a magnetic flux from a recording medium, preventing the magnetic flux from leaking into a region other than the detecting element, and restricting a magnetic signal to be read by the detecting element in a linear direction. In recent years, in a recording medium such as a hard disk or the like, a recording density, a reproducing speed of a signal recorded on the recording medium, and a frequency of a reproducing signal have been increased. Therefore, due to a magnetic resistance effect (MR effect) of each of the lower shield layer and the upper shield layer, reading precision of the detecting element may be reduced or noise may overlap reading signals. For this reason, it is preferable that each of the lower shield layer and the upper shield layer have an area as small as possible and a simple shape.
In the magnetic head device disclosed in JP-A-2001-307307, the lower shield layer and the upper shield layer integrally extend backward, thereby forming a conductive layer. As a result, the lower shield layer and the upper shield layer have complicated planar shapes that may cause noise. Further, since each of the lower shield layer and the upper shield layer is formed of a soft magnetic material, such as an alloy of Ni.Fe (alloy of nickel and iron), a direct current resistance is high, and a detection output calculated from the resistance variation may be reduced.
In the magnetic head device disclosed in JP-A-2002-25017, since the lower shield layer is formed to have a larger size than the upper shield layer, it is likely to provide unbalanced shielding effects between the lower shield layer and the upper shield layer, which affects reading precision of the detecting element. Further, noise may occur due to the large and complicated shape of the lower shield layer. Furthermore, via-hole conductors are formed in the lower shield layer and the upper shield layer, and a lead layer that is electrically connected to the lower shield layer and a lead layer that is electrically connected to the upper shield layer are formed at locations higher than the upper shield layer. Thus, the size of the entire magnetic head device is increased.